The field of the subject invention is the mixing of viscous material in a transfer pipe so as to reduce nonuniformities in the physical properties of the materials resulting from a lack of turbulence in the viscous flow. Reducing temperature nonuniformities across a viscous flow profile is of particular importance.
Devices of the prior art have attempted to solve the problems of nonuniformities in the flow of viscous material with varying degrees of success, depending on the nonuniformity being remedied. For example, mixers have been designed to invert the locations of an inner concentric half and an outer concentric half such that the inner becomes the outer and vice versa. Such a mixer is used to remedy a situation where, due to velocity gradients from axis to periphery, polymer material in the outer concentric half of a transfer pipe has remained in the transfer pipe longer than the polymer in the inner concentric half of the transfer pipe. In polymerization reactions such a situation allows the polymer in the outer concentric half of the transfer pipe to polymerize to a much higher molecular weight than the material in the inner concentric half. By inverting the locations of the two concentric halves at approximately midstream, the two halves spend equal time in the transfer pipe and are thus polymerized to equal molecular weights. This inversion, however, does not remedy any problems which may be caused by cross stream temperature variation. In that case such an inversion simply results in an inversion of the temperature profile of a cross section of the polymer flow.
Other mixers of the prior art simply divide flowing viscous material in a transfer pipe into a few layers and recombine these layers at the exit end of the mixer. For this layering to be effective in eliminating cross-section temperature variations, it would need to be repeated many times before cross-section temperature homogeneity could be achieved, thus requiring a number of mixers end to end in the transfer pipe.